LOCATION RED HILL CAEstablished Series
TAXONOMIC CLASS: Fine-loamy, mixed, active, mesic Ultic Palexerolls
TYPICAL PEDON: Red Hill clay loam - forested. (Colors for dry conditions unless otherwise noted).
O1--2 to 0 inches; mixed litter of needles and leaves.
A11--0 to 3 inches; strong brown (7.5YR 5/6) clay loam, dark reddish brown (5YR 3/3) moist; massive breaking to medium granular structure; mixed soft and slightly hard, very friable, slightly sticky and slightly plastic; few fine roots; common tubular pores; slightly acid; few rodent burrows; abrupt wavy boundary. (2 to 5 inches thick).
A12--3 to 16 inches; yellowish red (5YR 4/8) clay loam, dark reddish brown (5YR 3/3) moist; massive breaking to fine granular structure; slightly hard, very friable, slightly sticky and slightly plastic; abundant fine and medium roots; many very fine and fine tubular and interstitial pores; slightly acid; few worm burrows; diffuse wavy boundary. (10 to 15 inches thick).
B1--16 to 35 inches; yellowish red (5YR 5/6) clay loam, dark reddish brown (2.5YR 3/4) moist; massive breaking to medium and fine granular structure; slightly hard, very friable, sticky and plastic; few medium, abundant very fine and fine roots; many very fine and fine tubular and interstitial pores; medium acid; diffuse wavy boundary. (16 to 34 inches thick).
B21t--35 to 50 inches; yellowish red (5YR 5/6) heavy clay loam, dark reddish brown (2.5YR 3/4) moist; massive breaking to medium and fine granular structure; slightly hard, very friable, sticky and plastic; few medium, plentiful very fine and fine roots; common fine tubular and interstitial pores; medium acid; diffuse wavy boundary. (8 to 16 inches thick).
B22t--50 to 62 inches; yellowish red (5YR 5/6) clay, dark reddish brown (2.5YR 3/4) moist; massive; slightly hard, friable, sticky and plastic; few coarse, plentiful fine roots; common fine tubular and interstitial pores; many moderately thick clay films on ped faces and in pores; few fine gravels; medium acid; clear, wavy boundary. (7 to 15 inches thick).
B3t--62 to 74 inches +; yellowish red (5YR 5/8) clay, dark reddish brown (2.5YR 3/4) moist; massive; hard, friable, sticky and plastic; few coarse, plentiful fine roots; common fine tubular and interstitial pores; common thin clay films on ped faces; medium acid (pH 6.0); few concretions one to three millimeters in diameter.
TYPE LOCATION: In Sonoma County, California, on Red Hill in the SW corner of the SW 1/4 of the NW 1/4 of sec 29, T.8N, R.9W, 50 percent slope under Douglas fir and California myrtle.
RANGE IN CHARACTERISTICS: The solum to the bottom of the argillic horizon is more than 5 feet thick. The A horizons range in color from brown to yellowish red when dry. They have hues of 7.5YR and 5YR, values of 4 or 5 and chromas of 6 to 8. Moist colors are dark reddish brown in hues of 5YR with value of 3 and chroma of 4. The texture is clay loam and gravelly or cobbly clay loam, structure is massive to weak granular and reaction is slightly acid. The Bt horizon colors are yellowish red when dry. They have 5YR hue, value of 5 and chromas of 6 to 8. Moist colors are dark reddish brown with 5YR or 2.5YR hue, value of 3 and chromas of 3 and 4. Textures are heavy clay loam and clay, structure is weak granular or massive, consistence is slightly hard to hard and reaction is medium acid to slightly acid.
COMPETING SERIES: These include the Aiken, Boomer, Melbourne, Parrish, Rescue, and Sites series. The Aiken soils have loam A horizons and dark red (moist) clay Bt horizons that are very strongly acid in the lower part. The Boomer soils are moderately deep, have gravelly loam A horizons and dark reddish brown (moist) gravelly clay loam Bt horizons. The Melbourne soils have medium acid A horizons and strongly acid Bt horizons. Rescue soils have reddish brown, medium acid loam A horizons and dark red and yellowish red (moist) medium acid sandy clay loam Bt horizons. Sites soils have reddish brown A horizons and strongly acid, red clay Bt horizons. Parrish soils have brown A horizons with chromas of 2 to 4 and a lithic contact to metasedimentary rock at depths less than 50 inches.
GEOGRAPHIC SETTING: The Red Hill soils occur on strongly sloping to steep uplands under hardwoods and conifers. Underlying rock is basic igneous and is metamorphosed in places. Elevations range from 1000 to 2000 feet and the climate is subhumid mesothermal with mean annual rainfall of 35 to 50 inches, with warm, dry summers and cool, wet winters. Mean annual temperature is about 55 degrees F.; average January temperature about 42 degrees F., and an average July temperature about 72 degrees F.
GEOGRAPHICALLY ASSOCIATED SOILS: Red Hill soils occur in the same general areas as the Josephine, Sites, and Boomer soils.
DRAINAGE AND PERMEABILITY: Well or moderately well drained, moderate permeability and medium to rapid runoff.
USE AND VEGETATION: Used mostly for forestry. Natural vegetation consists of Douglas fir, California myrtle, oaks, and associated shrubs. A few areas on gentler slopes have been cleared and planted to irrigated pasture and orchards.
DISTRIBUTION AND EXTENT: In Sonoma and Napa counties, where they are moderately extensive (over 10,000 acres).
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California
SERIES PROPOSED: Sonoma County, April 1965.
REMARKS: The Red Hill series was formerly classified in the Reddish Brown Lateritic group. The soils have ochric epipedons, argillic horizons with a base saturation less than 75 percent and an A1 horizon with color values less than 3.5.
OSED scanned by SSQA. Last revised by state on 4/65.